TrainingPeaks Jargon Buster

TrainingPeaks Jargon Buster

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In addition to the TrainingPeaks videos, below are some definitions of some of the key metrics you may come across when using TrainingPeaks to analyse, understand and plan your training. You can go as in depth as you wish, so all of these abbreviations may not be relevant to you, but will help you to understand what is possible.


Training Stress Score (TSS) is a quantifiable score of the training load that a workout incurs. It is a combination of intensity, variability and duration of a session. It was originally a metric only available to power meter users but can now be calculated from heart rate data also.

TSS is calculated using a very simple scoring system. Integral to this calculation is your Functional Threshold Heart Rate (FTHR) or Functional Threshold Power (FTP), which you will have discovered at the start of our plans by conducting our Threshold Test. FTHR is the heart rate you could theoretically maintain for an all-out 1-hour effort and FTP is the equivalent power. If you performed such an effort, this would give a TSS of 100.

For an hour session, if your FTHR and FTP are correct, 100 is the maximum score you can attain. You can earn more than 100 TSS in a single workout if the duration is longer than an hour.


If you are using a power meter, Average Power (AP) is simply the average wattage that you put out for the duration of the ride.


AP does not give a true reflection of the physiological demands of a ride. There are many variable factors that affect your rides: wind, hills, accelerations, steady tempo, descents, etc. To take these into account, an adjusted method of quantifying power for analysis was devised and this is Normalized Power (NP). Normalized Power combines two factors. 

First, the fact that physiological responses to rapid changes in intensity follow a time course that is predictable.  Secondly, the fact that many physiological responses (e.g. lactate production, glycogen utilisation, etc) are not linear when related to exercise intensity. An example could be a rider competing in an hour long circuit race and a similar duration flat time trial. It is likely that the AP of the circuit race will be significantly lower than the TT because of sitting in the wheels and coasting around tight corners.

However, the multiple accelerations and sprints involved in a circuit race will be reflected in the NP, which will be very similar to the value given to the time trial. This shows, that despite the disparity in AP, the physiological demands of both rides wherever similar and illustrates that NP is basically an estimate of the power that you could have maintained for the same physiological “cost” if your power output had been constant.


Variability Index (VI) is calculated by dividing NP by AP and shows how evenly paced a ride was. Going back to our example of a circuit race a time trial, for his circuit race, our rider had an AP of 220 W and an NP of 300 W, giving a VI of 1.36. In his time trial, his AP was 294 W and his NP was 300 W, showing a far more evenly paced ride with a VI of 1.02.


The Intensity Factor, which can be shown for any workout or part of a workout, is the ratio of NP to the rider’s FTP. So, for an hour’s flat time trial without many bends, these two figures should closely correlate and yield an IF close to 1.0. IF is used to calculate TSS and, as for an hour’s effort it shouldn’t exceed 1.0 if FTP is accurate, is a useful tool for tracking a rider’s FTP.


Velocità Ascensionale Media or VAM is the average rate of climb for a ride or a section of a ride expressed in vertical metres per hour (Vm/h). During Stage 10 of the 2015 Tour De France, on the 15.3 km climb to La-Pierre-Saint-Martin, Chris Froome’s VAM was 1602 VM/h.

All of the metrics above are available for free on TrainingPeaks Basic Athlete Edition but, if you choose to upgrade to the Premium Athlete Edition, you unlock more in-depth session analysis and also the incredibly powerful Performance Management Chart (PMC). See below.


The Performance Management Chart (PMC) allows you to log and track TSS from every session and see its accumulative effect on your fatigue, fitness and form. Especially powerful is the ability to plot the theoretical TSS of future sessions. This allows you to take the guess work out of tapering and ensure you have the best possible form for your key events. The PMC does this by tracking three key variables.


Acute Training Load (ATL) is the short term effects of workouts done in the last 7 days and is a reflection of your fatigue.


Chronic Training Load (CTL) is the cumulative effect of training done in the last 42 days, this is your fitness.


The Training Stress Balance (TSB) is the difference between CTL and ATL from the previous day. This calculation of Fitness minus Fatigue is an indicator of that crucial and previously intangible aspect of cycling performance, Form.

During a heavy training block you will be accumulating both Fitness (CTL) and Fatigue (ATL) and, although you will be getting fitter, because of the Fatigue, this won’t necessarily be reflected in your performances in racing and training. It is only when you decrease the training, during a recovery week or as part of a pre-event taper, that Fatigue will fall and your Fitness will be able to manifest as Form.


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